package leetcode;

/**
 * 221. 最大正方形
 * 在一个由 '0' 和 '1' 组成的二维矩阵内，找到只包含 '1' 的最大正方形，并返回其面积。
 * <p>
 * <p>
 * <p>
 * 示例 1：
 * <p>
 * <p>
 * 输入：matrix = [["1","0","1","0","0"],["1","0","1","1","1"],["1","1","1","1","1"],["1","0","0","1","0"]]
 * 输出：4
 * 示例 2：
 * <p>
 * <p>
 * 输入：matrix = [["0","1"],["1","0"]]
 * 输出：1
 * 示例 3：
 * <p>
 * 输入：matrix = [["0"]]
 * 输出：0
 */
public class MaximalSquare {

    public int maximalSquare(char[][] matrix) {
        if (matrix == null || matrix.length == 0) {
            return 0;
        }
        int row = matrix.length;
        int col = matrix[0].length;
        int max = 0;

        // row 行 col 列节点作为 右下角最大的正方形
        int[][] dp = new int[row][col];


        for (int i = 0; i < row; i++) {
            for (int j = 0; j < col; j++) {
                if (matrix[i][j] == '1') {
                    if (i == 0 || j == 0) {
                        dp[i][j] = 1;
                    } else {
                        dp[i][j] = Math.min(Math.min(dp[i - 1][j - 1], dp[i - 1][j]), dp[i][j - 1]) + 1;
                    }
                    max = Math.max(max, dp[i][j]);
                } else {
                    dp[i][j] = 0;
                }
            }
        }
        return max * max;
    }
}
